The present invention concerns a starter for an internal combustion engine that comprises a starter motor, a drive shaft capable of being driven by the starter motor, and a driven shaft that is mechanically linked with the drive shaft and is displaceable in the direction of its longitudinal axis, which said driven shaft is equipped with a pinion capable of being pushed into mesh with a flywheel ring gear of the internal combustion engine, whereby a pushing-forward of the driven shaft to engage the pinion in the flywheel ring gear takes place by means of an element located on the stator of the starter motor that executes a turning motion around the motor axis when the starter motor is energized.
“Inertia-drive” starters are widespread as starters for internal combustion engines. These inertia-drive starters have an electrical starter motor, the drive shaft of which is mechanically linked with a driven shaft that is displaceable in the direction of its longitudinal axis. On the end furthest from the starter motor, the drive shaft is equipped with a helical spline, on which a driving element of the driven shaft is turnably and displaceably located. This driving element of the driven shaft is interconnected via a roller-type overrunning clutch with a shaft comprising the pinion. When the starter motor is switched on, the driven shaft—with the driving element, the roller-type overrunning clutch, and the pinion shaft—are pushed forward in such a fashion that the pinion meshes with a flywheel ring gear of the internal combustion engine. The mechanical meshing function usually takes place by means of a mechanical relay that usually performs the switching function for the starter motor as well. This combination of pinion-engaging and switching function requires that a starter relay be attached to the starter. Since the starter is located in the crumple zone of a vehicle, there is a danger that, if an accident occurs, parts of the starter relay supplied with battery voltage can come into contact with the grounded vehicle body, which would cause a short circuit. A previously-disclosed starter is made known in DE 196 25 057 C1, for example.
A starter that functions without an attached starter relay that carries out the pinion-engaging function of the starter is based on the older German application 100 16 706.3. This starter functions according to the “braking-inertia drive” principle. The starter motor comprises a pole tube that executes a turning motion around the motor axis when the motor is energized. This turning motion of the pole tube starts a braking mechanism that exerts braking torque on the driving element of the driven shaft. This braking torque causes the driving element to be advanced by the helical spline on the drive shaft of the motor, so that the pinion of the starter engages in the flywheel ring gear of the internal combustion engine. According to the exemplary embodiments of the older German application, the braking device comprises either a brake drum interconnected with the driving element, against which said brake drum a stop block is pressed, or it comprises a pawl that is capable of being moved against a disk interconnected with the driving element with frictional engagement, whereby braking torque is exerted on the driving element by means of the positive connection between the pawl and the disk. For the stop block or the pawl to change position, a force must be exerted in the radial direction relative to the driving element, which said force is derived from the turning motion of the pole tube by means of a mechanism.